tablet pro

but pressing and holding on the Tablet Pro button locks the movement of the cursor until the Tablet Pro button is released.

Yes this is normal input behavious, pressing and holding on the screen anywhere will result in the touch being the primary cursor and the pen input will not work.

If I press and hold the button and then tap with the pen on the screen at a point different to the original position when i pressed the Tablet Pro button then it will 'jump' to the rotation of the camera that would have happened if it had been moving with the cursor.

What if you tap the screen first to initiate the cursor as the pen. Then press a touch button with finger. that is how i perform it.